[InstCombine] Introducing Aggressive Instruction Combine pass (-aggressive-instcombine).

Combine expression patterns to form expressions with fewer, simple instructions.
This pass does not modify the CFG.

For example, this pass reduce width of expressions post-dominated by TruncInst
into smaller width when applicable.

It differs from instcombine pass in that it contains pattern optimization that
requires higher complexity than the O(1), thus, it should run fewer times than
instcombine pass.

Differential Revision: https://reviews.llvm.org/D38313

llvm-svn: 323321

1 files changed, 1 insertions, 0 deletions

diff --git a/llvm/tools/opt/opt.cpp b/llvm/tools/opt/opt.cpp
index c1c84844a4a..e03f6cee39f 100644
--- a/llvm/tools/opt/opt.cpp
+++ b/llvm/tools/opt/opt.cpp
@@ -395,6 +395,7 @@ int main(int argc, char **argv) {
   initializeAnalysis(Registry);
   initializeTransformUtils(Registry);
   initializeInstCombine(Registry);
+  initializeAggressiveInstCombinerLegacyPassPass(Registry);
   initializeInstrumentation(Registry);
   initializeTarget(Registry);
   // For codegen passes, only passes that do IR to IR transformation are